What Is Cancer?

The process of cell growth in the body is normally an orderly one. Cells grow and divide as necessary to produce more cells as they are needed. Cells that are old or damaged die, and are replaced with new cells.

In cancer, something has gone wrong with this process. The cell's DNA has been damaged. DNA is a substance found in every cell in the body that directs the cell's functioning and reproduction. Cell DNA may be damaged by environmental agents, such as radiation (including excessive sunlight), viruses, chemicals, and tobacco smoke. Cells with damaged DNA may also be inherited from one's parents.

Normally, if a cell has damaged DNA, it either repairs it or dies. But in cancer, the damaged cell starts to reproduce in an uncontrolled way, creating more abnormal cells. It outlives the normal cells around it and forms a tumor (a lump or mass).

Not all tumors are invasive. Benign tumors may simply be removed and are unlikely to grow back again. Malignant tumors, however, are cancerous, and they may start to invade surrounding tissues. By entering the bloodstream or the lymph system, cancer cells can spread throughout the body.

Types of Cancer

Cancer is not one disease. There are more than one hundred different types of cancer, and they all behave differently. Liver cancer, for instance, grows at a different rate than colorectal cancer, and responds to different treatments.

Cancer is named after the site where it originates, no matter where it spreads. Breast cancer that has spread to the lungs is termed metastatic breast cancer, not lung cancer. Although there are many different types of cancer, they can all be divided into five main categories:

• Carcinoma. Cancer that begins in epithelial cells (cells that form the skin or tissues that line or cover internal organs)
• Sarcoma. Cancer that begins in connective tissue (such as bone, cartilage, fat, muscle, and blood vessels)
• Leukemia. Cancer that starts in blood-forming tissue (like bone marrow)
• Lymphoma and myeloma. Cancers that begin in the cells of the immune system
• Central nervous system cancers. Cancers that begin in the tissues of the brain or spinal cord

Cancers of the Breast

Most breast cancers are carcinomas, meaning they arise in the epithelial cells lining the ducts or the lobules. Cancers may begin in nonepithelial parts of the breast, such as the blood vessels or the connective tissue, but they are much less common than epithelial cancers.

The majority (80-85%) of breast cancers arise in the cells lining the mammary ducts. This type of cancer is called ductal carcinoma. Most of the remaining cases of breast cancer arise in the cells lining the lobules, termed lobular carcinoma. Medullary, mucinous, and tubular carcinomas are rare forms of breast cancer.

In Situ and Invasive Cancer

Breast cancers are classified as in situ or invasive (sometimes called infiltrating).

• Carcinoma in situ occurs when cancer cells grow inside ducts or lobules but don't invade adjacent fatty tissues. ("In situ" is Latin for "in place.")
• Invasive carcinomas break out of the ducts or lobules and penetrate surrounding tissue. This gives the cancer the opportunity to metastasize (spread) by entering the lymphatic system or blood vessels and travelling to other organs or bone tissue.

Types of Breast Cancer:

Ductal Carcinoma

• Ductal Carcinoma In Situ (DCIS). DCIS is cancer than remains confined with the mammary ducts and is the most commonly diagnosed noninvasive breast cancer. It is sometimes referred to as a precancerous condition, as it may be a precursor to invasive ductal carcinoma. There are often no symptoms. If DCIS remains confined, it is easily treated. Treatment is usually lumpectomy, possibly followed by radiation and sometimes chemotherapy.
• Invasive (infiltrating) ductal carcinoma (IDC). IDC begins in a mammary duct, breaks through the wall of the duct, and penetrates into the surrounding fatty tissue of the breast. This is the most common type of invasive breast cancer: about 80-85% of invasive breast cancers are IDCs. IDC may metastasize to other parts of the body.

Lobular Carcinoma

• Lobular carcinoma in situ (LCIS). LCIS is a noninvasive cancer that begins in the lobules. It does not break through the lobular walls, but may be a precursor to invasive lobular carcinoma. LCIS is usually treated by lumpectomy, sometimes followed with radiation.
• Invasive lobular carcinoma (ILC). ILC is an invasive cancer that begins in the breast's milk-producing glands (lobules). It's often harder to detect ILC by mammogram than IDC. About 10% of invasive breast cancers are ILCs. Like IDC, it can spread to other parts of the body.

Inflammatory Carcinoma

• Inflammatory carcinoma an uncommon (1-3%) but aggressive form of breast cancer. It may start under the skin in the soft tissues of the breast, or it may arise in the skin itself. It can cause the skin to have an orange peel appearance (peau d' orange) and become reddened. Unlike ductal and lobular cancers, it is treated first with chemotherapy and then with surgery.

Medullary Carcinoma

• Medullary carcinoma is an invasive cancer with special features that distinguish it from other forms of breast cancer. It forms a well-defined boundary between tumor tissue and normal tissue, its cells are unusually large, and immune system cells are present at the edges of the tumor. About 3-5% of invasive breast cancers are medullary carcinomas. The prognosis (outlook) for medullary carcinomas is usually better than for the more common types of invasive breast cancer.

Tubular Carcinoma

• Tubular carcinoma is a type of invasive ductal breast carcinoma. It is called tubular because the cells, when viewed under a microscope, resemble small tubes. About 2% of all invasive breast cancers are tubular carcinomas. They generally have a better prognosis than the more common invasive breast carcinomas.

Paget's Disease of the Nipple/Areola

• This type of breast cancer starts in the breast ducts and spreads to the skin of the nipple and then to the areola. It's almost always associated with DCIS or IDC. The skin of the nipple and areola often appears crusted, scaly, and red, with areas of bleeding or oozing. It is rare, accounting for only about 1% of all cases of breast cancer. It is usually treated with mastectomy.

Mucinous (Colloid) Carcinoma

• A rare type of invasive breast cancer formed by mucus-producing cancer cells. The prognosis for this type of breast cancer is generally better than for the more common types of invasive breast cancer.

Risk Factors

A risk factor is anything that increases the chances of getting a disease. No one knows exactly what causes breast cancer, and why some people with few risk factors may develop the disease, and other people with many risk factors may not. Some risk factors are controllable, some aren't. Although there is not 100% sure way of preventing breast cancer, it is possible to reduce your chances of getting breast cancer by reducing or eliminating the risk factors that you can control.

Risk Factors You Can't Control

• Gender. Women have a 100-times greater chance of developing breast cancer than men.
• Age. Almost 80% of breast cancers occur in women over age 50.
• Genetics. About 5-10% of breast cancers are thought to be hereditary and due to gene mutations (changes) inherited from a parent. The most common inherited mutations are those of the BRCA1 and BRCA2 genes.
• Family history of breast cancer. Having a mother, sister, or daughter with breast cancer doubles a woman's risk.
• Personal history of breast cancer. Having had breast cancer triples or quadruples the chances of developing another tumor. (This is different from recurrence.)
• Race. In the US, white women have the highest chance of developing breast cancer, while African-American women have a greater chance of dying from it. Asian, Hispanic, and Native-American women have a lower risk of developing and dying from breast cancer.
• Dense breasts. Women with dense breast tissue (tissue that has more glandular than fatty tissue) have a higher risk of breast cancer.
• Early or late menstruation. Women who began their periods early (before age 12) or who had a late menopause (after age 55) have a slightly greater risk of breast cancer. This may be because these women have a greater number of menstrual periods during their lifetimes.
• Previous chest radiation. Having had chest radiation for a different condition (eg, Hodgkin's disease) significantly increases risk of breast cancer.
• DES exposure. Women who took diethylstilbestrol (DES) during pregnancy, and women whose mothers took it during pregnancy, may have a slightly higher risk of breast cancer.

Risk Factors You Can Control

• Alcohol. Women who have one alcoholic drink a day have a very small increase in risk. Women who have 2-5 drinks daily have about 1.5 times the risk of women who drink no alcohol.
• Children. Not having children, or having a first child after age 30, slightly increases breast cancer risk.
• Recent oral contraceptive use. Use of oral contraceptives slightly increases risk, but risk declines once their use is stopped.
• Hormone therapy. Long-term use of combination hormone-replacement therapy for the relief of symptoms of menopause increases breast cancer risk.
• Not breastfeeding. Breastfeeding may lower breast cancer risk, especially if done for a long period of time. This may be because doing so reduces the number of menstrual periods a woman has during her lifetime.
• Overweight or obesity. Being overweight or obese increases breast cancer risk, especially after menopause.
• Lack of physical activity. Being inactive increases the risk of breast cancer. As little as 1